1. Field of the Invention
This invention relates to position detecting apparatus and, more specifically, to position detecting apparatus using a unique pulse pattern to define and continuously verify a respective position detection.
2. Description of the Related Art
In many control applications it is necessary to know the position of a movable portion of the system. Several methods have been used to accomplish such an objective. A first group of methods provides an absolute position of the system at any given point. These sensors typically utilize a potentiometer which provides a resistance value corresponding to a specific position. The advantage of this type of system is that there is no loss of reference such that the system requires calibration. A second group of position sensors are relative in nature. These systems have a zero or calibration point and generate pulses as the system moves from this point of calibration. The system position is determined by adding or subtracting the pulses that are encountered or generated as the system moves from the zero position. Typically, these pulses are provided by use of a hall effect sensor, an optical sensor or a make-or-break switch configuration. The advantage of such a system is its simplicity over the absolute sensors. The disadvantage is that if the pulses are counted in the wrong direction, the system will not correctly correspond to the position indicated. Another disadvantage is that if a stored position is incorrect, the system has no means of self calibration to provide continuous error correction.